Apparatus for mixing liquids and gases



1955 D. G. MELROSE APPARATUS FOR MIXING LIQUIDS AND GASES 2 Sheets-Sheet1 Filed Dec. 23, 1952 MM m+ E M Ml um r 5 m p Oct. 25, 1955 D. G.MELROSE 2,721,732

APPARATUS FOR MIXING LIQUIDS AND GASES Filed Dec. 23, 1952 2Sheets-Sheet 2 INl/L'N TOR DEM/s GRA HA M Ma ROSE 3 81 IQ m- A TT'ORNEYs United States Patent APPARATUS FOR MIXING LIQUIDS AND GASES DenisGraham Melrose, Putney, London, England, as-

signor to National Research Development Corporation, London, England, acorporation of Great Britain Application December 23, 1952, Serial No.327,527 Claims priority, application Great Britain January 3, 1952 6Claims. (Cl. 261-33) The present invention relates to improved apparatusfor quickly bringing a gas into intimate contact with a liquid and,although not exclusively limited thereto, is particularly suitable foroxygenating blood.

In order to carry out an examination of, or surgical operation upon, apatients heart in substantially bloodless conditions, it has alreadybeen proposed to by-pass the heart and lungs by taking blood from thepatient on the venous side and returning it on the arterial side,placing in the by-pass apparatus which re-oxygenates the blood andreturns it at an appropriate rate through the remainder of the body.

A known way of re-oxygenating blood is to spread out the blood into athin film and then fiow oxygen over the film, but in the past severaldifficulties have been experienced in carrying out such operations,among which may be mentioned that of providing an adequate rate of flowof oxygenated blood whilst avoiding undue foaming, haemolysis or otherdeleterious effect upon the blood, and

of accurately controlling the rate of flow of the blood to the needs ofthe patient.

It is an object of the present invention to provide apparatus which inthese and several other respects is an improvement on that knownhitherto.

A preferred form of the invention will now be described with referenceto the accompanying diagrammatic drawings in which:

Figure 1 is a side elevation of a blood oxygenator,

Figure 2 is a right-hand end elevation, on a somewhat larger scale, ofthe same apparatus,

Figure 3 is a side elevation of one of several rings forming part of theoxygenator.

Figure 4 is a section on the line IVIV of Figure 3,

Figure 5 is a side elevation of one of several annuli making up theoxygenator,

Figure 6 is a section on the line VI-Vl of Figure 5,

Figure 7 is an elevation showing one ring and one annulus placed inface-to-face contact,

Figure 8 is a section on the line VIIIVIII of Figure 7,

Figure 9 is a sectional elevation, on an enlarged scale, through aportion of the oxygenator shown in Figure 1,

Figure 10 is a section on the line X-X of Figure 9,

Figure 11 is a section on the line XIXI of Figure 10, and

Figure 12 is a circuit diagram illustrating apparatus for controllingthe oxygenator of Figure 1.

The apparatus illustrated in Figures 1 to 11 comprises a transparentcylindrical shell 20 which is 30 inches long and of internal diameter 8inches. It is made of a material which may be readily sterilised, suchas compressed nylon. At its two ends it is closed by centrally aperturedplates 21 and 22 each of external diameter 10 inches. The end-plates aremounted for rotation upon two pairs of rollers, such as those shown at23, 24 and 25, with the axis of the cylindrical shell inclined to thehorizontal at a small angle which may be 5 for example.

Fixed on the left-hand end plate 21, and spaced from it, is a paralleldriving plate 26 forming part of a continuously variable friction gearthe other wheel 27 of which can be moved up and down a rod 28 with theaid of a manually operable screw 29 threaded through a yoke 30 whichcarries the friction Wheel 27. The friction Wheel 27 is splined on therod 28 and is rotated, through worm gear 31 at the lower end of the rod,by a fractional H. P. electric motor 32. The motor may be, for example,of 3& H. P. running at 960 R. P. M. and the speed of rotation of thecylindrical shell may be varied to anything between about 24 to R. P. M.by moving the friction wheel 27 radially with respect to the drivingplate 26.

Fixedly secured within the cylindrical shell 20 are a plurality ofring-shaped plates, also made of nylon, and arranged so that theirapertures constitute a passage from end to end of the cylindrical shell.The plates are of two somewhat similar kinds and the two kinds arearranged alternately throughout the length of the cylinder. Henceforththe two kinds will be called rings (of which there may be 77) and annuli(of which there may be 76) in order to distinguish them one from theother.

A ring is shown in detail at 33 in Figures 3 and 4. It is circular andof external diameter such that it is a sliding fit in the cylindricalshell 20. It is formed with a central aperture 34 of 4% inches diameterand is V inch thick. It is also formed with eight equi-angularlydisposed holes such as those shown at 35.

Each annulus 36 (Figures 5 and 6) is similar in shape to a ring exceptthat it is inch thick and is formed with a circular aperture 37 of 5%inches diameter, the centre of which is eccentric by 1 inch.

As stated above these rings and annuli are arranged alternately in thecylindrical shell 20 and Figures 7 and 8 illustrate one of each as theyare arranged in the cylindrical shell, the annulus being in front of thering in Figure 7. It will be seen that when .so placed together theyform a crescent-shaped rabbet 38 which, When another ring is added tothe other side of the annulus, is converted into a crescent-shapedtrough of the kind shown at 39A or 39B in Figure 9.

The rings and annuli are also arranged in groups of two kinds whichalternate along the length of the cylindrical shell 20. One groupconsists of five rings and five annuli having the maximum depth of thecrescent-shaped troughs 39A arranged at 6 oclock in end view, as shownin Figure 10. The other group consists of five rings and five annuliarranged with the maximum depth of the troughs (393 in Figure 9) allarranged at 12 oclock in end view, as shown in Figure 11.

The rings and annuli are assembled in this manner upon four chromiumplated steel rods such as those shown at 40 and 41 in Figure l and aretightened together with the aid of four nuts (42, 43, 44 and 45 inFigure 2) so as to be liquid tight. They are then fitted into thecylindrical shell 20 (after the end-plate 22 has been removed) upon fourother chromium plated steel rods 46, 47, 48 and 49, whereupon theend-plate 22 is assembled on these four rods and tightened on to the endof the cylindrical shell with the aid of suitable nuts.

The end-plate 22 is formed with an aperture 50 through which are passedan inlet pipe 51, for blood, dipping into the rear or upper end of theoxygenator, an outlet pipe 52, also for blood, dipping into the forwardend of the oxygenator, an outlet pipe 53 for oxygen and a pipe 54 withthe aid of which the depth of blood in the oxygenator may be measured.

The left-hand end plate 21 is also formed with an aperture through whichis passed a pipe 55 serving to suply oxygen to the oxygenator.

It will be seen that the cylindrical shell, rings, annuli and pipes areall completely detachable for cleaning.

The cylindrical shell, rings and annuli thus together constitute a kindof elongated cylinder-like shell or hollow body, the general axis ofwhich is inclined to the horizontal and through which cylinder-likeshellthe blood may be flowed downwardly under gravity while oxygen ispassed in contra flow over the surface of the blood.

In effect the internal shape of the cylindrical shell 2% hasbeenaltered, by the addition of the rings and annuli, and the containerhas been converted to an elongated cylinder-like shell or hollow body,the outer surface of which is cylindrical but the internal surface ofwhich is in the form of a plurality of end-to-end cylinder-likeassemblies all having their'axes eccentric with respect to apredetermined axis, namely the axis of the external cylindrical surfaceof the shell. Furthermore, the axis of one cylinder-like assembly isdisplaced by 180 with respect to each of the two assemblies adjacent toit and with reference to the predetermined axis.

The apparatus so far described is used in the following 'way:

I left-hand end of the oxygenator whence it is pumped out,

at the same rate as it enters, through the outlet pipe 52.Simultaneously a stream of oxygen is passed continuously through theoxygenator by way of the pipes 55 and 53, in the opposite direction tothe flow of blood.

Consider an instant at which blood drops into the oxygenator when agroup of five crescent-shaped troughs 39B are immediately above the endof the inlet pipe 51, i. e. are in the 12 oclock position shown inFigure 11 and at the right-hand end of Figure 9. Then the incoming bloodfalls on to what is approximately a cylindrical surface and tends toflow by gravity towards the adjacent group of crescent-shaped troughs37A which are in the 6 oclock position as shown in Figure 10 and at theleft-hand end of Figure 9. In fact, however, before the blood can passfrom one group to the next the oxygenator has made sevcral revolutions.Nevertheless the tendency is always for the blood to fiow from right toleft through the oxygenator. Each time the blood rests in a group of 6oclock troughs 39A, the two sides of each thin ring 33, and the floorsof the troughs between these rings, become coated with blood and a thinfilm is carried up to the 12 oclock position and down again as theoxygenator rotates. In this way a thin film of blood is maintained incontact with the oxygen at a capacity which, when the oxygenator isrotated at its maximum speed, gives a minute area of 120 square metres.

Some of the blood is continually being spread into a film in this way,carried up in to the stream of oxygen, and then returned to a pool lyingin a 6 oclock set of crescent-shaped troughs. At the same time eachlittle pool remaining in the 6 oclock position is alternately raised tolie on a cylindrical surface shown at the righthand end of Figure 9 andis then lowered into a trough, the blood flowing down through theoxygenator simultaneously with this continuous cycling of the blood intofilms and back into a pool. In effect therefore theseveral pools in agroup are alternately formed and emptied in alternating sequence, andthe fact that adjacent groups are displaced angularly by 180 ensuresthat as pools are formed in one group they are being emptied in anadjacent group.

The present invention possesses several advantages as compared withknown apparatus for achieving the same end, not the least of which isthat it avoids the use of plates having edges which cut through theblood at high speed, in a direction transverse to the edges, and in thisway damage the blood. It will be seen that, in the present apparatus,the edges of the rings are the only ones which move through the bloodand each edge moves not only at a relatively low speed, but also in adirection approximately parallel with itself, thus avoiding damage tothe blood.

Furthermore, less blood (approximately 50% less) is required to fill theoxygenator to working level, better mixing of the blood is achieved, thewhole of the available film-forming surface of the apparatus is broughtinto use irrespective of the volume of blood passing through in unittime, and the capacity of the machine is greater.

Apparatus for controlling the rate of flow of blood through theoxygenator is shown in Figure 12.

The patient is represented at 56, the venous and arterial sides being atthe left and right-hand respectively.

Blood is drawn from the venous side of the patient by a pump 57 drivenby a motor 58 under the control of a controller 59 which is bothmanually and automatically operable and which supplies power to themotor 58 independently of the mains voltage. The rate of supply can bedetermined either by a manual setting 60 or by electric signalsgenerated in a manner to be described.

The pump 57 passes the blood from the patient into the oxygenator whichmay be identical with that'illustrated in Figures 1 to 11.

Re-oxygenated blood is extracted from the oxygenator, and returned tothe patient on the arterial side, by a pump 61 the pressure of which isrecorded by an electromagnetic manometer 62, whilst a similar manometer63 records the suction produced by the pump 57.

A level recorder 64 gives a continuous record of the level of blood inthe oxygenator and also provides signals when the level rises or fallsto danger limits.

The pump 61 is driven by a motor 65 under the control of a controller 66similar to 59 and having a manual setting 67.

Mixers 68 and 69 are electronic valve-operated units -which combine thesignals from the manometers and deliver master signals to the electroniccontrollers 59 and 66 and also to alarm devices 70 and 71 which includesteady green and winking red lamps together with buzzers, as desired, toprovide visible and/0r audible warning of any dangerous condition,approaching or present.

The rate at which blood is supplied to and withdrawn from the patient,i. e. the rate at which it passes through the oxygenator, normallyshould remain constant and a large part of the function of the controlapparatus is to ensure this.

An example of the way in which this control apparatus is used is asfollows:

Suppose the output of the pump 57 falls, the controller 59 is such as toboost it up. If, however, the boosting is still insufficient, an alarmis provided at 70, in which case any one of a variety of expedients maybe adopted. For example, the mixer 68 may operate on 69 so as to reducethe output of pump 61, via controller 66 and motor 65, until the bloodrates at opposite ends of the oxygenator are again equalized. As analternative the control apparatus may be operated manually until thedesired functioning is arrived at, whereupon it may be re-set to operateautomaticaly.

Generally, the control apparatus should be of the greatestflexibility sothat, in order to compensate for a change in any one of these factors,any or all of "the others-may be'adjusted either automatically ormanually.

If desired a'by-pass circuit 73 may be provided with the aid of whichsaline may be continuously circulated through the oxygenator, and airbubbles in the various pipes opened to the atmosphere and thus excludedfrom What I claim is:

1. Apparatus for bringing a liquid and gas into intimate contact,including an elongate hollow body member, means for supporting saidmember so that it is inclined to the horizontal, means for rotating saidmember about a central axis, inlets and outlets to said member such thata liquid may be flowed through it under gravity and a gas may be passedthrough it above the liquid, the internal shape of said member being inthe form of a plurality of groups of annuli having inner cylindricalsurfaces the axes of which are eccentric with respect to said centralaxis, the axis of said groups of annuli being displaced 180 with respectto that of each adjacent group of annuli with reference to said centralaxis, and a plurality of spaced rings, each formed with an aperturecoaxial with said central axis, arranged at spaced intervals throughoutthe length of said groups of annuli so as to subdivide said groups.

2. Apparatus for bringing a liquid and gas into intimate contact,including a hollow elongate cylinder-like shell, means for supportingsaid shell so that it is inclined to the horizontal, means for rotatingsaid shell about a central axis, inlets and outlets to said shell suchthat a liquid may be flowed through it under gravity and a gas may bepassed through it above the liquid, the internal shape of said shellbeing in the form of a plurality of sets of alternately arrangedcrescent-shaped troughs, those of one set being arranged with themaximum depth of trough angu' larly displaced with respect to themaximum depth of an adjacent set.

3. Apparatus as claimed in claim 2, wherein the angular displacementbetween the maxima is 180.

4. Apparatus for bringing a liquid and gas into intimate contact,including a hollow elongate cylinder-like shell, means for supportingsaid shell so that it is inclined to the horizontal, means for rotatingsaid shell about an axis, inlets and outlets to said shell such that aliquid may be flowed through it under gravity and a gas may be passedthrough it above the liquid, the internal shape of said shell being inthe form of a plurality of sets of alternately arranged annuli, theinner cylindrical surfaces of which are eccentric with respect to saidaxis, the eccentricity of one set being angularly displaced with respectto those of another set, and a plurality of rings each formed with anaperture coaxial with said axis and ar ranged at spaced intervalsthroughout the length of said shell.

5. Apparatus for bringing a liquid and gas into intimate contact,including a cylinder-like shell having its axis inclined to thehorizontal, means for rotating said shell about its axis, inlets andoutlets to said shell such that, while it is rotating, a liquid may beflowed through it under gravity and a gas may be passed through it abovethe liquid, a plurality of centrally apertured rings and a plurality ofeccentrically apertured annuli stacked within said shell, the annulibeing arranged in sequentially arranged groups the eccentricities ofsuccessive groups being displaced angularly and a ring being locatedbetween each adjacent pair of annuli.

6. Apparatus as claimed in claim 5, including two groups of annuli theangular displacement between adjacent ones of which is References Citedin the file of this patent UNITED STATES PATENTS 1,253,401 Lorimer Ian.15, 1918 1,592,231 Stroder July 13, 1926 2,575,688 Smith Nov. 20, 1951FOREIGN PATENTS 138,694 Germany Feb. 12, 1903 348,244 Great Britain May14. 1931

1. APPARATUS FOR BRINGING A LIQUID AND GAS INTO INTIMATE CONTACT,INCLUDING AN ELONGATE HOLLOW BODY MEMBER, MEANS FOR SUPPORTING SAIDMEMBER SO THAT IT IS INCLINED TO THE HORIZONTAL, MEANS FOR ROTATING SAIDMEMBER ABOUT A CENTRAL AXIS, INLETS AND OUTLETS TO SAID MEMBER SUCH THATA LIQUID MAY BE FLOWED THROUGH IT UNDER GRAVITY AND A GAS MAY BE PASSEDTHROUYGH IT ABOVE THE LIQUID, THE ITERNAL SHAPE OF SAID MEMBER BEING INTHE FORM OF A PLURALITY OF GROUPS OF ANNULI HAVING INNER CYLINDRICALSURFACES THE AXES OF WHICH ARE ECCENTRIC WITH RESPECT TO SAID CENTRALAXIS, THE AXIS OF SAID GROUPS OF ANNULI BEING DISPLACED 180* WITHRESPECT TO THAT OF EACH ADJACENT GROUP OF ANNULI WITH REFERENCE TO SAIDCENTRAL AXIS, AND A PLURALITY OF SPACED RINGS, EACH FORMED WITH ANAPERTURE COAXIAL WITH SAID CENTRAL AXIS, ARRANGED AT SPACED INTERVALSTHROUGHOUT THE LENGTH OF SAID GROUPS OF ANNULI SO AS TO SUBDIVIDE SAIDGROUPS.